Alpha-amino acids are the basic building blocks of peptides and proteins, which are responsible for the structure and function of most living things. They are extensively employed as chiral templates and subunits in the asymmetric construction of many biologically and pharmacologically active compounds. Nonproteinogenic examples are increasingly utilized to study enzyme mechanisms and to modify and enhance protein activity. Alpha-amino phosphonic acids are structural analogs of amino acids and as such exhibit a broad range of biological activities: enzyme inhibitors, antitumor agents, anti-bacterial agents, and fungicides. The principal objective of the proposed work is to develop practical and efficient methodology for the asymmetric synthesis of functionalized alpha amino acids and alpha amino phosphonic acids by exploiting the diastereoselective addition of CN and phosphite anions to chiral nonracemic sulfinimines [N-sulfinyl imines, R'S(o)N=CR2R3]. Important advantages conferred by the N-sulfinyl group include (i) powerful stereodirecting effects, (ii) activation of the C-N double bond toward addition, and (iii) facile auxiliary removal and hydrolysis of the N-sulfinyl alpha amino nitrile and alpha amino phosphonate to amino acids and amino phosphonic acids under such exceedingly mild conditions that racemization does not occur. Complementary studies will focus on the synthesis and regioselective and stereoselective ring-opening reactions of N-sulfinyl aziridine 2-phosphonates as sources of novel alpha amino phosphonic acids. The imino-Diels-Alder reactions of 2H-azirine phosphonates, a new chiral dienophile, will be exploited as sources of novel aziridine 2-phosphonates and azabicyclic systems; the latter compounds are important chiral building blocks and exhibit a range of biological activities. Such studies are expected to provide new information on the chemical reactivity/selectivity of the phosphonate group as compared to carboxylate esters. Concurrently we will employ this chemistry in syntheses of biologically relevant, functionalized alpha amino acids and alpha amino phosphonates that are difficult or impossible to prepare via other methodologies. Targets include cyclic, unsaturated, and, beta substituted derivatives (beta amino, beta hydroxy, and beta fluoro).